14-6
OPERATION HRX217HYA • HRX217HZA
3. HYDROSTATIC TRANSMISSION
The hydrostatic transmission features infinitely variable speed control by controlling the hydraulic flow rate. The
operator can select the optimum ground speed by simply moving the shift lever.
OPERATION PRINCIPLE
<Pump cylinder side>
The pump cylinder side consists of the pump control bowl, which can change its angle, and the pump cylinder
incorporating seven pistons.
The engine speed is transmitted to the pump shaft by way of the driven pulley, and it turns the pump cylinder. As the
pump control bowl changes its angle, the pistons in the pump cylinder start a reciprocating motion.
PISTON
SPRING
PUMP CYLINDER
PUMP CONTROL
BOWL
CASE
PUMP SHAFT
PUMP SHAFT
PISTON
PUMP CYLINDER
PUMP SHAFT
INLET STROKE
(Pistons rise)
To motor
cylinder
PISTON AT TDC
(Top Dead Center)
PISTON AT
TDC (Top
Dead Center)
Rotation
direction
Rotation
direction
DISCHARGE STROKE
(Pistons compress)
From motor cylinder
PISTON AT BDC
(Bottom Dead
Center)
PISTON
AT BDC
(Bottom
Dead
Center)
(Viewed from the pump control bowl side)
PUMP
CONTROL
BOWL